This invention relates to bearing blocks or sheaves which are designed primarily for use on sailing vessels.
Modern sailing vessels use a variety of bearing blocks or rotatable sheaves to control lines or cables attached to the sails and various parts of the rigging. A bearing block comprises a line-receiving sheave rotatably mounted between a pair of side plates, with the side plates being attached to the vessel or rigging by means of a shackle or other attachment means. The term "sheave" is also generally used to denote the combination of an outer annular rotating member having a line receiving groove, and an inner circular fixed plate member, with bearings between the inner and outer members.
With the increased technical sophistication of racing sailboats, the total weight and bulk of the fittings mounted on the boat become an important consideration. Weight of fittings at or above the deckline contribute to healing momentum, and bulky fittings increase windage. Thus, it is desirable to provide fittings, such as bearing blocks and sheaves, which have a minimal surface area and profile, as well as a high strength to weight ratio.
It is common practice in the case of bearing blocks and sheaves to provide a plurality of openings therein to reduce total weight. A point is reached, however, where the size or total area of the openings reduce the working strength of the fitting.